arm64: dma-mapping: always clear allocated buffers

commit 6829e274a623187c24f7cfc0e3d35f25d087fcc5 upstream.

Buffers allocated by dma_alloc_coherent() are always zeroed on Alpha,
ARM (32bit), MIPS, PowerPC, x86/x86_64 and probably other architectures.
It turned out that some drivers rely on this 'feature'. Allocated buffer
might be also exposed to userspace with dma_mmap() call, so clearing it
is desired from security point of view to avoid exposing random memory
to userspace. This patch unifies dma_alloc_coherent() behavior on ARM64
architecture with other implementations by unconditionally zeroing
allocated buffer.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
[will: ported to 3.14.y]
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index 3974881388bbbe24be2f4c4822ac5adbd30c634a..b76159a153a5b27aa205dca1e878008a1632a2a0 100644 (file)
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -54,8 +54,7 @@ static void *arm64_swiotlb_alloc_coherent(struct device *dev, size_t size,
 
                *dma_handle = phys_to_dma(dev, page_to_phys(page));
                addr = page_address(page);
-               if (flags & __GFP_ZERO)
-                       memset(addr, 0, size);
+               memset(addr, 0, size);
                return addr;
        } else {
                return swiotlb_alloc_coherent(dev, size, dma_handle, flags);